IMSA's first practice session for the WeatherTech SportsCar Championship's visit to Watkins Glen gave the 38 entries plenty to deal with as wet and dry conditions posed a challenge around the 3.4-mile circuit.

The specter of rain hung over the one-hour session and finally arrived with less than 10 minutes on the clock. In the dry, JDC-Miller Motorsports fired a shot at the dominant Daytona Prototype internationals as Stephen Simpson went fastest overall in the WEC P2-spec ORECA 07-Gibson. The South African's best lap of 1m35.491 withstood a number of runs by DPi drivers, and once the rain started falling, Ryan Dalziel's second-best lap on the No. 2 Tequila Patron ESM Nissan Onroak DPi (+0.039s) and Joao Barbosa's No. 5 Action Express Racing Cadillac DPi-V.R (+1.322s) locked in the top three.

"We don't want to be the best of the rest," Simpson told IMSA Radio. "Honestly, the JDC-Miller Motorsports guys have been doing a great job. Now our expectations are to come here and run for a podium; anything less would be a disappointment."

The Prototype class opened the event with vehicular adversity as 30 percent of the entries dealt with major issues. The No. 90 Visit Florida Racing Riley/Multimatic Mk 30-Gibson pulled off course with some form of a leak at the back of the WEC LMP2, the No. 22 Nissan Onroak DPi was sidelined by an alternator belt problem, and the No. 70 Mazda RT24-P only managed a single lap before brake problems intervened and ended its session.

Performance Tech Motorsports' mastery of PC continued as Pato O'Ward (1m39.741s) was a full 1.8 seconds faster in his No. 38 ORECA FLM09-Chevy than the No. 20 BAR1 Racing entry in the three-car class.